TCP Window Scaling

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Level 1

22 points

TCP Window Scaling

Hello,

I'm trying to diagnose a rather wierd problem (partial data transfer) and would like to find out

1.) if OS X does dynamic TCP window scaling?

and if so,

2.) how do I disable it?

Thanks. 🙂

-- James

intel mini, Mac OS X (10.4.9)

Posted on Apr 11, 2007 2:15 PM

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Answer 1

Camelot

Level 9

59,833 points

Apr 12, 2007 12:05 PM in response to jbarros

Yes, Mac OS X supports dynamic window scaling.

Off hand I don't know how to disable it, though. The only sysctl variable that seems relevant is net.inet.tcp.win scalefactor which OMM defaults to 5. It's possible that setting it to 0 disables it, but I haven't tried:

<pre class=command>sudo sysctl -w net.inet.tcp.win scalefactor=0</pre>

However, I do wonder why you think this is the problem. Window scaling may impact performance (e.g. cause slow performance) but it's not likely to terminate connections mid-stream. Things like MTU are far more likely candidates.

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